The invention concerns a linear drive, comprising primary part or a secondary part arranged on a slide block, wherein the slide block is movable on a guide-rail system, as well as a stationary secondary part or primary part, as the case may be, which operates together with the primary part or secondary part arranged on the slide block in such a way that the slide block is movable on the guide-rail system.
Furthermore the invention concerns a process for assembly and dismantling of this linear drive, wherein this process in this case in particular refers to the assembly or dismantling of the primary part or secondary part onto or from a movable slide block.
Prior art linear drives are wide spread in engineeing. For example they are used in machining centres or machine tools, in order to move and position the lathe spindle at higher speed or with greater precision. The secondary part in such instances comprises an arrangement of magnets having alternating polarity. The secondary part is for example arranged to be stationary and operates in conjunction with the primary part. The primary part comprises an electromagnetic drive, in which the current conduction is used to generate a magnetic field, which operates in conjunction with the magnetic field of the secondary part so that the slide block moves on the guide-rails.
The invention is described as follows such that the primary part is located on the slide block and the secondary part is stationary. However the invention is not limited to this arrangement. In the same way it is possible to arrange for the secondary part (ie the arrangement of the magnets) to be movable on the slide block and the primary part to be stationary.
One or more guide-rails may be arranged, for example, as the guide-rail system. To achieve higher efficiency the gap between primary part and secondary part may be designed to be relatively small. This gap ultimately defines the drive efficiency and with this also the power consumption for a movement of the system.
With an arrangement such that the movement travel of the linear drive runs in a horizontal plane, the primary part is located for example beneath the slide block. The lathe spindle, eg a cutting tool machine, is constructed on the slide block. The primary part in this case is connected to the slide block with fixing means, for example with screws. The total assembly attains a considerable weight of up to several tonnes. If the primary part is then to be serviced or to be changed on account of tool wear, this can pose some problems to the fitter. The primary part is constructed beneath the slide block so that this cannot be reached easily. Also it is not always possible to lift up the machine tool associated with it. At the same time it should be noted that in addition to the weight of the slide block and the mounted assembly the magnetic attraction of the secondary part still acts upon all magnetisable elements, which increases the force which would be needed to lift off the guide block from the guide-rail system.
The costly dismantling of the linear drive leads to long maintenance times accompanied by long down-times of the machine tool, which is usually undesirable.
The invention had as its task to improve a linear drive as initially described, to the effect that the time for changing the primary part, and with this the down-time of the plant fitted with the linear drive, is reduced.
The invention here assumes as a starting point a linear drive as initially described, ie a linear drive comprising a primary part and a secondary part, one of which is mounted on a slide block and the other of which is stationary. The invention proposes a that a spacer block is arranged between the primary part or the secondary part and the slide block, which is able to be then from the slide block when dismantling the primary part or the secondary part and the distance between part and secondary part is thus increased. In the gap so formed a means of transport is introduced, upon which the part or the secondary part is lowered and then moved out. From this the process also arises according to the invention for dismantling a primary part or secondary part from a slide block on a movable guide-rail system, wherein a spacer block is arranged between the primary part or the secondary part and the slide block and the primary part or secondary part is held onto the slide block by a means of fixing, which are freed for dismantling so that the spacer block is able to be taken off and the primary part or the secondary part is then moved against the slide block by the fixing means or other positioning means, whereby a gap arises between primary part and secondary part so that a means of transport is arranged in this gap and the fixing means of the primary part is released completely in order to move the primary part away from the slide block using the transport means.
On account of the high magnetic force acting between the primary part and the secondary part, care should be taken that primary and secondary parts do not come into contact with one another or lie flat on one another, since a movement of both elements relative to one another is then only possible with high energy cost, or is impossible. The transport means introduced into the so formed gap consists in this case most favourably of a non-magnetic material and acts as spacer between both of the magnetically attractive elements. On account of the residual gap there will be no adhesion of the two elements, both elements remaining movable one with another.
In the case of the process for dismantling according to the invention the spacer block is preferably held on the slide block by the same fixing means which also fix the primary part to this. Next the spacer block is extracted in order to create space between primary part and slide block, which, after the primary part is moved relative to the slide block, serves to increase the gap between primary and secondary parts so that a useful gap arises.
At the same time it is not necessary that all fixing means are involved, rather it is possible that only a few fixing means serve to fix the primary part to the slide block. At this point the fixing means are at first opened a little and through this the primary part lowered by a few tenths of a millimeter or moved against the secondary part, in order to remove the spacer block sideways. If the spacer block is removed, the primary part is again moved against the slide block with the help of the fixing means, which are then tightened again, or by further means of assistance, eg., positioning means, as a result of which the gap forms. For the idea according to the invention it is not critical that a noticeable gap of a few millimeter remains in the opening condition; it is however essential for the idea according to the invention that the gap between primary part and secondary part is increased by the extraction of the spacer block. In tis way it is also possible that the distance between primary part and secondary part is virtually zero.
The arrangement according to the invention is however limited not only to a process for dismantling the primary part but also concerns also in the inverse sense a process for assembly of a primary part or secondary part on a slide block which is movable on a guide-rail system, wherein the part or secondary part is positioned on or adjacent the transport means under the slide block, wherein the primary part or secondary part is held by the fixing means or positioning means of the slide block and the transport means is removed from the primary part or secondary part, wherein the primary part or secondary part is then removed from the slide block slightly by the fixing means or positioning means, in order to introduce and arrange the spacer block between primary part and slide block and subsequently the primary part and slide block are connected firmly together with the fixing means.
The invention is not limited to the arrangement of the primary part or secondary part above or at the side of the secondary part or primary part. The invention is able to be used in the same way with linear drives whose slide block is able to be processed in a horizontal, vertical or other inclined plane. Provided that the phrase xe2x80x9cunder the slide blockxe2x80x9d relates to an arrangement, in which the primary part or secondary part is located between slide block and secondary part or primary part.
During assembly or dismantling, the manipulation gap, hence the available height for introduction and insertion or extraction of the primary part, is deliberately increased by the arrangement according to the invention and then when the primary part is positioned, the superfluous gap is concealed by the spacer block. In case the primary part is to be removed the process is reversed and firstly the available gap height is increased by removal of the spacer block. The gap thickness gained is used in order to introduce a transport means, upon which the primary part is then lowered, laid or supported, in order to transport this away from the linear drive.
It is possible by means of the proposal according to the invention to change the primary part within a shorter time, without dismantling the complete linear drive or removing the slide block from the guide-rail system at the same time. The work reduction resulting from this also leads to distinctly shorter down-times for the machine and consequently to a higher efficiency, of the plant equipped with such a linear drive.
The invention is described as follows, such that the primary part is located on the slide block, and the secondary part is stationary. The invention however is not limited to this arrangement. It is possible in the same way to arrange the secondary part (thus the arrangement of the magnets) to be movable on the slide block and the part arranged to be stationary.
In one variation according to the invention a blank spacing plate is provided for use as the spacer block. The blank plate exhibits a certain thickness which together with the existing gap between primary and secondary parts pre-defines the available gap thickness for a transport means.
By this means a further advantage is provided also in the assembly of the linear drive. The spacer blocks or also the blank plates are provided in a set of various thicknesses, in order to optimise particularly the distance between primary and secondary parts by use of these. At the same time it is possible to equalise the manufacturing tolerances as a result of this.
In addition to the use of blank plates it is also possible to use spacer blocks of different forms, for example bushes and such like, or also spacer blocks with variable thickness.
Furthermore it is beneficial if the spacer block is composed of one or more parts. It is advantageous for an even support for the primary part if the spacer block is arranged to be as flat as possible between the two elements. It is of advantage particularly in the case of larger arrangements, to form the spacer block from several components, so as not to have individual elements which are too bulky. In this it is to be noted fat the installed drive may be difficult to access under some circumstances and that it is therefore more beneficial to use several smaller spacer blocks, rather than one large block.
In a further development of the invention slit-sped recesses are provided in the spacer block or blank plate for fixing means, which are provided for between slide block and primary part. The spacer block is usually built in at right angles to the effective direction of the fixing means between primary part and slide block. The spacer block is able to be inserted along these slit-shaped recesses on the fixing means and offers a correspondingly larger bearing surface especially in the case of larger flatter spacer blocks. In this respect the spacer block may be designed alternatively for insertion without the appropriate recesses. The arrangement of the spacer block between primary part and slide block is then chosen, so that the fixing means do not interfere, as the spacer block exhibits smaller dimensions than the spacing between two fixing means, so that it may be inserted between the fixing means.
More favourably screw connections are provided for as fixing means and/or positioning means. It is also an intention of the invention that the function of the positioning means is simultaneously undertaken by the fixing means. The use of screw fixings is advantageous to the effect that a relatively exact positioning is possible by appropriate choice of the thread-pitch, especially when removing the spacer block. Adjusting gauges, tensioning tools or other such tools may be used as positioning means.
It has proved beneficial if the spacer block exhibits a thickness of a few millimeters, eg two to ten millimeters. The gap resulting from this is adequate to introduce an appropriate transport means and to assemble and dismantle the and secondary parts respectively.
In a preferred arrangement of The invention the slide block is designed to be able to be processed in a horizontal, vertical or inclined plane. In all these cases the arrangement according to the invention achieves the ability to access the primary pat or secondary part which is to be removed.
It is also possible for the slide block to be located above or below the primary part or secondary part, as appropriate. If the slide block is located above the primary part or secondary part the slide block is held by the superposition of gravity with the magnetic attraction forces on the guide-rail system However an xe2x80x9cover-head arrangementxe2x80x9d is also realisable, wherein for example the guide-rail system is arranged above the slide block and thereby the primary part or secondary part is also arranged above the slide block. The idea according to the invention van also be used with the xe2x80x9cover-head arrangementxe2x80x9d. Apart from the weight of the elements to be removed, the primary or secondary part, which can amount to around 50 kg to 100 kg, a magnetic force of about 1 tonne to 2 tonne acts upon this element. It is however entirely possible that when dismantling a xe2x80x9csuspendedxe2x80x9d assembled linear drive the primary part becomes attracted by the secondary part and consequently the same problem arises, as with a xe2x80x9chorizontalxe2x80x9d arrangement. However the use of the spacer blocks is advantageous even in this arrangement, which allows the introduction of a transport means, in order to remove the primary part or secondary part respectively.
It is proposed in the process according to the invention that a transport means is used to transport the primary part. It is beneficial here for the transport means to be made from non-magnetic material, for example cardboard, paste-board, plastics or similar. The transport means is in this case for example a support plate which is laid upon the secondary part and upon which the primary part moves by sliding. The advantage of such an arrangement is that a cardboard or other similar support plate is almost always available in a workshop. At the same time the surface finish of cardboard, paste-board or plastics in particular is so soft, that contaminants, for example splinters or such like will not lead to damaging the secondary part surface. On account of the high magnetic forces between primary and secondary parts metal chips which are present between these two part, would scratch the surface of primary/secondary parts when moving.
Apart from use of cardboard, paste-board, plastics etc., it is also possible to employ non-magnetic metals, such as copper or brass. With an appropriate arrangement it is also possible for example to equip the transport means with wheels in order to enable smooth running.
The invention also embraces machine tools which are equipped with a linear drivexe2x80x94as described. The linear drives are particularly well known in the case of machine tools as rapid and precise positioning means. Here it is beneficial for these to be employed as cutting tools, for example in machining centres or automatic milling machines.